Objective To examine the hypothesis that nitric oxide plays a role in the pubertal increase in LHRH release in non-human primates. ABSTRACT:Using a push-pull perfusion method the effects of L-arg, the substrate required for nitric oxide synthesis, on LHRH release in vivo were examined in female monkeys at various pubertal stages. L-arg at 0.1 nM, 10 nM and 1 mM was infused into the stalk-median eminence for 10 min at 90-min intervals and perfusates were collected in 10-min fractions for 14 h. In prepubertal monkeys L-arg at all doses resulted in significant increases (p<0.01) in LHRH release peaking at 10 min after infusion. Similarly, in monkeys at early and midpubertal stages L-arg at all doses stimulated LHRH release (p<0.05) at 10 min after infusions. The LHRH responses to L-arg at all doses tested were similar within pubertal stage and the magnitude of the L-arg-induced LHRH release was comparable in both stages. Neither infusion of vehicle or D-arg induced any significant effects. These results suggest that L-arg does stimulate LHRH release and nitric oxide may be important for the pulsatility of LHRH release in the non-human primate. However, the fact that L-arg induces similar LHRH responses in animals at both prepubertal and pubertal stages suggests that nitric oxide may not be critically involved in the mechanism triggering puberty. Keywords Nitric oxide, LHRH release, L-arginine, D-arginine